Re: [PATCH 03/18] drm/mediatek: redefine mtk_ddp_sout_sel

From: Nicolas Boichat
Date: Mon Dec 24 2018 - 23:08:02 EST


On Mon, Dec 24, 2018 at 6:52 PM Yongqiang Niu
<yongqiang.niu@xxxxxxxxxxxx> wrote:
>
> This patch redefine mtk_ddp_sout_sel

Can you describe a bit more why you are making this change?

> Signed-off-by: Yongqiang Niu <yongqiang.niu@xxxxxxxxxxxx>
> ---
> drivers/gpu/drm/mediatek/mtk_drm_ddp.c | 32 ++++++++++++++++++++------------
> 1 file changed, 20 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_ddp.c b/drivers/gpu/drm/mediatek/mtk_drm_ddp.c
> index adb37e4..592f852 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_ddp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_ddp.c
> @@ -405,21 +405,27 @@ static unsigned int mtk_ddp_sel_in(enum mtk_ddp_comp_id cur,
> return value;
> }
>
> -static void mtk_ddp_sout_sel(void __iomem *config_regs,
> - enum mtk_ddp_comp_id cur,
> - enum mtk_ddp_comp_id next)
> +static unsigned int mtk_ddp_sout_sel(void __iomem *config_regs,

You don't use config_regs anymore, drop it.

> + enum mtk_ddp_comp_id cur,
> + enum mtk_ddp_comp_id next,
> + unsigned int *addr)
> {
> + unsigned int value;
> +
> if (cur == DDP_COMPONENT_BLS && next == DDP_COMPONENT_DSI0) {
> - writel_relaxed(BLS_TO_DSI_RDMA1_TO_DPI1,
> - config_regs + DISP_REG_CONFIG_OUT_SEL);
> + *addr = DISP_REG_CONFIG_OUT_SEL;
> + value = BLS_TO_DSI_RDMA1_TO_DPI1;

You can directly return BLS_TO_DSI_RDMA1_TO_DPI1.

> } else if (cur == DDP_COMPONENT_BLS && next == DDP_COMPONENT_DPI0) {
> - writel_relaxed(BLS_TO_DPI_RDMA1_TO_DSI,
> - config_regs + DISP_REG_CONFIG_OUT_SEL);
> - writel_relaxed(DSI_SEL_IN_RDMA,
> - config_regs + DISP_REG_CONFIG_DSI_SEL);
> - writel_relaxed(DPI_SEL_IN_BLS,
> - config_regs + DISP_REG_CONFIG_DPI_SEL);
> + *addr = DISP_REG_CONFIG_OUT_SEL;
> + value = BLS_TO_DPI_RDMA1_TO_DSI;

I (kind of) understand the change above, as you still end up writing
BLS_TO_DSI_RDMA1_TO_DPI1 in DISP_REG_CONFIG_OUT_SEL.

This changes the behaviour, as now you only write
BLS_TO_DPI_RDMA1_TO_DSI to DISP_REG_CONFIG_OUT_SEL, but the previous
revision of the code would also write to DISP_REG_CONFIG_DSI_SEL and
DISP_REG_CONFIG_DPI_SEL. Why?

> + } else if (cur == DDP_COMPONENT_RDMA1 && next == DDP_COMPONENT_DSI0) {
> + *addr = DISP_REG_CONFIG_DSI_SEL;
> + value = DSI_SEL_IN_RDMA;
> + } else {
> + value = 0;
> }
> +
> + return value;
> }
>
> void mtk_ddp_add_comp_to_path(void __iomem *config_regs,
> @@ -434,7 +440,9 @@ void mtk_ddp_add_comp_to_path(void __iomem *config_regs,
> writel_relaxed(reg, config_regs + addr);
> }
>
> - mtk_ddp_sout_sel(config_regs, cur, next);
> + value = mtk_ddp_sout_sel(cur, next, &addr);
> + if (value)
> + writel_relaxed(value, config_regs + addr);

Why this change? I don't see mtk_ddp_sout_sel being used later in the
series, so I'm not sure why we don't directly write the value into the
register.



> value = mtk_ddp_sel_in(cur, next, &addr);
> if (value) {
> --
> 1.8.1.1.dirty
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